1. Field of the Invention
The present invention relates to an electrophotographic apparatus, for example, an electrophotographic copying machine, a printer employing an electrophotographic method or the like wherein at least one of the developing devices disposed along a photoreceptor is removable.
2. Description of the Prior Art
In the case where color-development is carried out by use of an electrophotographic apparatus comprising a plurality of developing devices along the surface of a photoreceptor, a developing device located at upstream of the remainings with respect to the direction of the rotation of the photoreceptor is usually used as a color-developing device, for example, red-color-developing device for the purpose of preventing toner color mixing. Accordingly, the developing device located at upstream of the other with respect to the direction of the rotation of the photoreceptor is conventionally removable in order to facilitate the exchange of toner color.
Meanwhile, in a developing device, there arises the problem that toner unused for the development scatters around the location between the photoreceptor and a casing of the developing device. A scattering toner forms powder smoke to rise up or falls down to a non-image portion on the surface of the photoreceptor. Particularly, in the above-mentioned electrophotographic apparatus comprising a plurality of developing devices, the scattering toner mixes into other developing devices or brings a fog in the non-image portion on the surface of the photoreceptor.
Therefore, a seal member for preventing toner scattering is usually arranged at a developing device in order to prevent toner from scattering by its contact with the photoreceptor. But in such electrophotographic apparatus, the seal member for the developing device located at downstream with respect to the direction of the rotation of the photoreceptor requires to be in contact with or out of contact with the photoreceptor in accordance with the attachment and the removal of the developing device located at upstream of the other with respect to the direction of the rotation of the photoreceptor. In other words, said upstream developing device must be attached following the retreat of the seal member arranged at the downstream developing device from the photoreceptor so as to prevent the seal member arranged at the downstream developing device from destroying a toner image developed by the upstream developing device. On the contrary, in the case of removal of the developing device located at upstream, the seal member arranged at the developing device located downstream must be brought into contact with the photoreceptor for preventing toner scattering.
Although the Japanese Patent Laid-open Application No. 62-211675 discloses an electrostatic latent image developing device wherein the seal member for the developing device located at downstream is caused to be in contact with or out of contact with the photoreceptor by use of a solenoid. However, the use of the electric member not only complicates the construction of said developing device but also disadvantages in term of cost.